Variable vane cascades

ABSTRACT

A VARIABLE AREA TURBINE NOZZLE RING HAS A FIRST SET OF FIXED VANES AND A SECOND SET OF VANES WHICH ARE MOVABLE TOWARD AND AWAY FROM THE THROAT OF THE NOZZLES BETWEEN THE OTHER SETS OF VANES SO AS TO VARY THE OUTLET AREA. THE SECOND SET OF VANES MAY MOVE AT BOTH ENDS OR AT ONLY ONE END.

United States Patent [72] Inventor Earle R. Wall, Jr. Indianapolis. Ind.

[21] Appl, No. 836.422

[22] Filed June 25, 1969 [45] Patented June 28, 1971 [73] Assignee General Motors Corporation Detroit, Mich.

[54] VARIABLE VANE CASCADES 3 Claims, 6 Drawing Figs.

[52] U.S.C1 415/161, 415/115 [51] 1nt.C1 ..F0ld 25/12, F04d 27/00 [50] Field of Search 230/114,

Primary Examiner-Henry F. Raduazo Anorneys- Paul Fitzpatrick and Jean L. Carpenter ABSTRACT: A variable area turbine nozzle ring has a first set of fixed vanes and a second set of vanes which are movable toward and away from the throat of the nozzles between the other sets of vanes so as to vary the outlet area. The second set of vanes may move at both ends or at only one end.

[5 6] References Cited UNITED STATES PATENTS A.P.C.

344.165 5/1943 Baj 415/160 L 1/ I I t z ,4 L

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l 3' z f/ PATENTEU JUN28 197-1 SHEET 2 [1F 2 JQr/ZWZZ/K az 750M A 7' TORNEY VARIABLE VANE CASCADES The invention herein described was made in the course of work under a contract or subcontract thereunder with the Department of Defense.

DESCRIPTION My invention is directed to variable area vane cascades such as turbine nozzles or stator rings of compressors and is particularly suited to arrangements wherein it is desirable to vary the area of a turbine nozzle without significantly affecting the direction of discharge of the gas from the nozzle.

Typical variable turbine nozzles include structures in which the vanes are rotatable about spanwise extending axes, or in which some part of the vane is so rotatable, or other structures in which shifting of one part of the vane with respect to the other creates a partial blocking, and so forth. The turbine nozzle which constitutes the preferred embodiment of my invention comprises a set of fixed fluid turning vanes which may generally follow known practice defining nozzles for the fluid tov flow from the nozzle to the turbine wheel. In addition to this, the nozzle includes a second set of vanes or throttling members which extend generally parallel to the first set of vanes and are movable generally in the direction of flow through the throats of the intervane passages of the nozzle. Means are provided to shift these secondary vanes or throttling members in unison. Also, in the preferred embodiment of my invention, the structure is such as to be well. adapted to provision of transpiration cooling on the surfaces of the nozzles which are particularly exposed to and scoured by the hot motive fluid.

The principal objects of my invention are to provide an improved cooled variable area turbine nozzle; to provide a variable area turbine nozzle in which throttling of flow is accomplished without significant change in the direction of discharge of the gas; to provide a variable area turbine nozzle that is of simple, reliable, and rugged structure; and, in general, to provide a turbine nozzle particularly suited to the requirements of high temperature turbomachinery in which some variation of flow area is desired.

The nature of my invention and the advantages thereof will be clear to those skilled in the art from the succeeding detailed description of preferred embodiments of the invention and the accompanying drawings thereof. The description and drawings are provided for the purpose of explaining the principles of the invention and are not to be construed in a limiting sense, as modifications of structure may be made without departing from the spirit of the invention.

Referring to the drawings, FIG. I is a sectional view through a turbine nozzle taken in a plane containing the axis of rotation of the turbine.

FIG. 2 is a partial sectional view taken on the plane in dicated by theline 2-2 in FIG. 1, with parts cutaway.

FIG. 3 is a fragmentary axonometric view of a turbine nozzle-facing.

FIG. 4 is a fragmentary axonometric view of a turbine nozzle mounting-ring.

FIG. 5 is a partial somewhat schematic view taken on a plane parallel to the axis of the turbine.

FIG. 6 is a view. similar to- FIG. 1 illustrating a second form of nozzle embodying myinvention.

The nozzle illustrated in-FIGSt l, 2, 3 and 4 forms a part of an-axial flow turbine which, as to'the structure not illustrated, may be-of any conventional'or standard construction; It may have structure such as are illustrated in my copendingapplication for Variable Turbine Nozzles Ser. No. 836,423 filed June 25, 1969. The turbine includes a case 5 with' a flange 6 to which is bolted the outer'shroud 7 of a turbine nozzle or'stator vane ring which also comprises an'inner shroud 8. anda ring of flowdirecting vanes or-airfoils 10. The outer shroud 7 includes a structural mounting ring ll.bolted toflange 6 and a porous facing definedby a forward or upstream ring 12and-a rear or downstream ring 14; the'latter being securedby bolts 15.to the' rear edge'of the mounting ring. The'upstream facing ring12 may be retained in a slot in a ring 16 bolted to flange 6.

The inner shroud 8 includes a mounting ring or structural ring 17 made up of a forward ring 18 and a rear ring 19. These have flanges which are bolted to an inner combustion chamber wall 20 which is fixed in the engine relative to the outer case 5. The inner shroud 8 also includes a forward porous facing ring 22 and a rear porous facing ring 23 which are held in place on the mounting rings 18 and 19, respectively, by spring clip rings 24, this arrangement for mounting the facing rings being described fully in my US. Pat. application Ser. No. 836,423.

The rear margin of the facing ring 22 has notches 26 and the forward edge of the ring 23 bears notches 27 which are contoured to respond to the outline or cross section of the vanes 10. The outer facing rings 12 and 14 are similarly cut out to accommodate the vanes. The vanes 10 have two flanges 28 at each end of the vane which embrace the edges of the facing rings at the cutouts 26 and 27 so that there is no significant path for leakage of air or gas through the connection between the vanes and facing rings.

Each vane is supported from the mounting rings 11 and 17 by a tubular spine 32 to which the concave and convex walls of the vane are welded, brazed, or otherwise fixed. The ends of this spine are flared into a rectangular or square cross section providing a head 34 received in a recess in the inner surface of ring 11 and a head 35 received in a recess or socket defined by notches 36 in the mating edges of the mounting rings 18 and 19. A strengthening flange 38 is provided around these notches.

In general, the structure so far described, apart from the arrangement of the porous facings which is the subject matter of my aforementioned copending application, may be regarded as conventional turbine nozzle structure and is merely the preferred environment of the improvement which is the subject matter of this patent application.

The vanes 10 define converging nozzles or flow paths 40 through which the gas is discharged from the structure ahead of the nozzle to the turbine rotor (not illustrated) downstream of the nozzle. According to my invention, a second group of vanes or throttling members is arranged alternating with the vanes 10 and movable so as to variably restrict the flow area of the nozzle.

A throttling member 42, which may be regarded as a vane of a second set, is mounted in the flow passage 40 between each pair of vanes 10. As will be apparent from the drawings, the vanes or throttling members 42 are of much smaller chord and thickness than the flow directing vanes. They are mounted so as to be movable toward and away from the throat or location of minimum area of the: passage or nozzle between adjacent vanes. Throttling member 42 preferably is a hollow tubular body of streamlined or, in other words, noncambered airfoil cross section. Each member 42 extends from outside the outer mounting ring 11 to the interior of the inner mounting ring 17. However, only the portion between the porous facings is of the airfoil shape.

As shown most clearly in FIG. 6 (which in other respects discloses a different embodiment of the invention), the throt tling member 42 has flanges 43 at each end which lie on either side of the facing'members'and serve to close the opening at 44 in the facings which provide some clearance from the throttling member so that it may move in the direction generally upstream and downstream of thepassage 40.

In theform illustrated in FIG. 1, the member 42 has outer and inner extensions 46 which extend through the mounting rings 11 and l7and are coupledto crank arms which support and adjust the members 42'. The inner extension 46 is mountedin a crank arm 47'fixed on a shaft 48'which extends through the spine 32 of the vane 10. The end of shaft 48 at the innershroud8 is journaledinthe end of spine 32 and the outer end of the shaft is journaledin'a boss 49 on the outer'mounting ring 11. An actuating arm'50 is integral with or fixed to the shaft 48. The outer extension46of the throttling member is mountedon arm 50. All of arms50 are coupled by suitable hearings to a unison ring 51 which extends around the axis of the nozzle and is coupled to suitable means by which it may be rotated to vary the position of members 42. Means for actuating the unison ring 51! may be of the nature of that described in my above-mentioned copending application. The extensions 46 may be fixed to the arms 47 and 50 so as to rotate with the shaft 48 or they may be mounted so they may rotate relative to these. Also, extensions 46 may be made rotatable with respect to members 42. The throttling member 42 may be arranged to weathervane or automatically align itself for direction of flow; or, if desired, it may be positively oriented by engagement in the outer and inner mounting ring or facing ring so that the throttling member is aligned by positive engagement with the fixed structure. The extensions 46 pass through an elongated hole 53 in the ring 19 and a similar hole in the ring 11. Any suitable guide structure may be provided to control the rotation of the extensions 46 or members 42.

As will be most clearly apparent from the schematic diagram of FIG. 5, the members 42 move upstream or downstream in the flow passages 40 as the unison ring is rotated, moving the arms 50 and 47 so as to move the throttling members. As each member moves toward or away from the nozzle throat, the area for flow is decreased or increased.

The throttling members 42 move so that they remain generally parallel to their original position, although it is possible to vary this relation to some extent by having different effective lengths of the arms 47 and the portion of the arms 50 which couple the extensions 46 to shaft 48.

FIG. 6 illustrates a simplified structure in which the movement of the throttling members 42 is a swinging movement about a fixed point in the inner shroud so that the radially inner end of the throttling member .moves relatively little as compared to the movement ofthe radially outer end. With this structure, there is less uniformity in the throttling from end to end of the vanes but this effect is not of particular importance in many cases. FIG. 6 eliminates the need for the shaft 48 and crank 47, but otherwise the structure may be substantially the same as that previously described. Correspond' ing parts shown in FIG. 6 have the same numbers as FIG. 1. In this case the throttling member 42 may have an inner extension 55 rotatably coupled by a pin 57 to a clevis on the portion 19 of the inner mounting ring. The radially outer end of the throttling member 42 bears a rod-like extension 58 which may be rectangular section and which is coupled to the arm 50 by a pin 59 engaging in a clevis 60. The extension 58 may be sufficiently limber to twist when the arm 50 is rotated through the small angle involved or the clevis 60 may be rotatably mounted on the arm 50. It will be seen, therefore, that the structure of HO. 6 is the same as that previously described except that the motion of the radially outer end of the throttling member 42 is substantially greater than that ofthe inner end.

It is to be understood that means for introducing cooling air behind the porous facings and into the interior of the vane are preferably provided. These may be of the same nature as those described in my copending application Ser. No. 836,423 and the nature thereof is immaterial to my present invention in a variable nozzle. Therefore, it will not be described herein in detail. lt may be pointed out, however, that cooling air may be admitted through holes 61 in the outer shroud and holes 62 in the inner facing. The ends of the vanes may be open to receive air from within the facing and discharge it through the surface of the vane, which may be porous.

It will be clear to those skilled in the art from the foregoing that l have devised practical and useful arrangements for varying the area of a turbine nozzle without adversely affecting flow or substantially disturbing the angle of discharge of the gas.

The detailed description of preferred embodiments of the invention for the purpose of explaining the principles thereof is not to be considered as limiting or restricting the invention, since many modifications may be made by the exercise of skill in the art.

1 claim:

1. A variable-area stator vane ring for a turbomachine comprising, in combination, first and second annular shrouds defining a fluid flow path between the shrouds, an annular cascade of fixed flow-deflecting vanes extending from shroud to shroud defining flow passages between adjacent vanes and adapted to determine the direction of fluid flow from the said passages, a set of streamlined throttling members extending generally parallel to the vanes, each throttling member being disposed between two adjacent vanes in a said passage, and means connected to the throttling members for concurrently moving the throttling members upstream and downstream in the passages while maintaining the setting of the throttling members substantially constant, so as to vary the effective area of the vane ring and maintain a substantially constant direction of flow from the passages.

2. A variable-area stator vane ring for a turbomachine comprising, in combination, first and second annular shrouds defining a fluid flow path between the shrouds, an annular cascade of fixed flow-deflecting vanes extending from shroud to shroud defining flow passages between adjacent vanes and adapted to determine the direction of fluid flow from the said passages, a set of streamlined throttling members extending from shroud to shroud generally parallel to the vanes, each throttling member being disposed between two adjacent vanes in a said passage, and means connected to the throttling members for concurrently translating the throttling members upstream and downstream in the passages while maintaining the setting of the throttling members substantially constant, so as to vary the effective area of the vane ring and maintain a substantially constant direction of flow from the passages, the last-named means including shafts extending through the vanes spanwise of the vanes and arms connecting the shafts to the throttling members.

3. A variable-area stator vane ring for a turbomachine comprising, in combination, first and second annular shrouds defining a fluid flow path between the shrouds, an annular cascade of fixed flow-deflecting vanes extending from shroud to shroud defining flow passages between adjacent vanes and adapted to determine the direction of fluid flow from the said passages, a set of streamlined throttling members extending from shroud to shroud generally parallel to the vanes, each throttling member being disposed between two adjacent vanes in a said passage, one end of each throttling member being pivotally connected to one said shroud, and means connected to the other ends of the throttling members for concurrently translating the other ends of the throttling members upstream and downstream in the passages while maintaining the setting of the throttling members substantially constant so as to vary the effective area of the vane ring and maintain a substantially constant direction of flow from the passages. 

